Fuel tanks can contain potentially combustible combinations of fuel vapors, oxygen, and ignition sources. To prevent combustion, inert gas, such as nitrogen-enriched air (NEA) or oxygen-depleted air (ODA), is introduced into the ullage of a fuel tank, in order to keep the oxygen concentration in the ullage below 12%. A variety of membrane-based technologies have conventionally been used to inert fuel tank air. Similarly, fire suppression systems, such as fire suppression systems deployed in aircraft cargo holds, can function with inert gas.